Depth API : CIDepthBlurEffect

After going through WWDC 2017 session materials, I came accrss Photo Filter sample code that uses depth deliveray.

What I want to do is, show depth blur on preview feed.

I notice that in order to accomplish this, there needs to be a Metal View. After delivering depth maps, run it thru "CIDepthBlurEffect" filter.

1. Can CIDepthBlurEffect be fast enough for preview? OR that filter is only ment to editing depth images after saved?
2. How come there is no information on "CIDepthBlurEffect" on Apple's Documentation?
3. Anyone can direct me to more resources that would help with above task (I already went thru WWDC 2017 session videos and sample code.)

Thanks in advance.